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Safety and acceptability of a baggy latex condom
ORIGINAL RESEARCH ARTICLE
Safety and Acceptability of a Baggy Latex Condom Maurizio Macaluso,* Richard Blackwell,† Bruce Carr,‡ Jareen Meinzen-Derr,* Michele Montgomery,* Micki Roark,‡ Murrill Lynch,† and Elizabeth M. Stringer† A total of 104 couples participated in a randomized crossover trial to compare a new baggy condom with a straightshaft condom produced by the same manufacturer. Participants completed a coital log after using each condom. All couples used five condoms of each type. Among 102 couples who did not report major deviations from the protocol, the breakage rate was eight of 510 (1.6%) for the baggy condom, and six of 510 (1.2%) for the standard condom (rate difference, RD ⫽ 0.4%, 95% confidence interval of the RD, CI ⫽ ⫺1.0%; ⫹1.8%). Slippage was reported in 50 baggy condom logs and in 58 standard condom logs; the slippage rate was 50 of 510 (9.8%) for the baggy condom, and 58 of 510 (11.4%) for the standard condom (RD ⫽ ⫺1.6%, 95% CI ⫽ ⫺5.4%; ⫹2.2%). Slippage was most often partial (⬍1 inch) and may not indicate condom failure. Severe slippage rates were 11 of 510 (2.2%) for the baggy condom, and 18 of 510 (3.5%) for the standard condom (RD ⫽ ⫺1.4%, 95% CI ⫽ ⫺3.4%; ⫹0.7%). The findings support the conclusion that the two condoms are equivalent with respect to breakage and slippage. The participants appeared to prefer the baggy condom, suggesting that the new product may be more acceptable to the public than the traditional straight-shaft condoms, and may be easier to use consistently over long time periods. CONTRACEPTION 2000;61:217–223 © 2000 Elsevier Science Inc. All rights reserved. KEY WORDS:
barrier contraception, contraceptive efficacy, phase I/II studies
Introduction
W
hen used consistently and correctly, the latex condom provides good protection against unintended pregnancy and against infection with sexually-transmitted pathogens, in-
*Department of Epidemiology and International Health, School of Public Health, University of Alabama at Birmingham, Birmingham, Alabama; †Department of Obstetrics and Gynecology, School of Medicine, University of Alabama at Birmingham, Birmingham, Alabama; and ‡Department of Obstetrics and Gynecology, School of Medicine, University of Texas Southwestern Medical Center, Dallas, Texas Name and address for correspondence: Dr. Maurizio Macaluso, UAB School of Public Health, MJH 108, 1530 3rd Ave South, Birmingham, AL 35294-2010; Tel.: (205) 934-7835; Fax: (205) 975-2435 Submitted for publication December 13, 1999 Revised February 7, 2000 Accepted for publication February 10, 2000
© 2000 Elsevier Science Inc. All rights reserved. 655 Avenue of the Americas, New York, NY 10010
cluding the human immunodeficiency virus (HIV).1 Despite large-scale efforts to encourage safer sex, consistent condom use is not widely practiced.2–5 For example, the latex condom was used as a contraceptive by only 19% of US women 15– 44 years of age who were at risk for pregnancy in the 1995 National Survey of Family Growth.3 The most common complaints among users are that condoms interrupt lovemaking and reduce sensation.6 Thus, the design and production of more acceptable condoms may play an important role in the promotion of condom use to larger segments of the population. Loose-fitting condoms seem to reduce interference with sensation during intercourse and may be more acceptable.1 We report the results of a phase I study of the acceptability and safety of a new baggy condom, compared with a standard straight-shaft condom.
Materials and Methods Study Design and Procedures To compare the newly designed baggy condom (X) with a straight-shaft, control condom (S) produced by the same manufacturer, we designed a prospective evaluation, according to a randomized cross-over design, of couples who used both condom types. A couple was eligible for participation in the study if the following conditions were met: 1) the woman’s age was 18 – 47 years; 2) the couple was in a mutually monogamous relationship during the previous 6 months; 3) the couple was using a method of birth control; 4) the couple was not using barrier contraception as the main birth control method; 5) neither partner had had sexually transmitted diseases during the previous 2 years; 6) neither partner was allergic to latex; 7) the couple maintained an average coital frequency of five acts of intercourse per month. A total of 100 couples were recruited at two centers. Four additional couples were added later at one center to compensate for known protocol deviations and to ensure that information would be obtained on a total of 500 condoms of each type. Interested subjects were recruited from among personnel at the participating centers and from the local communities ISSN 0010-7824/00/$20.00 PII S0010-7824(00)00097-4
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through advertising. Either partner was allowed to be the primary participant, but in most cases women responded to the advertising and participated in the study. The participant partner provided informed consent and was interviewed at entry to gather baseline information. Next, the paticipant was randomly assigned to begin either with the X condom or with the S condom. The two alternative use sequences are referred to as X-S and S-X. Each participant received five condoms of one type, and was instructed to complete a brief questionnaire for each condom used (referred to as the coital log) and to return the logs after completing use of the five condoms. The log requested detailed information about problems that may have occurred during intercourse. If condom breakage occurred, the participant was asked to report when the breakage was noted (while opening the package, during intercourse, before/after ejaculation, after withdrawal) and in which section of the condom (base, mid-section, tip). If slippage occurred, the participant was asked to report when it was noted (before entry, during intercourse, before/after ejaculation, during or after withdrawal), and the extent of the slippage (⬍1 inch down the penis shaft, ⬎1 inch but not completely off, or completely off the penis). The definition of breakage used in the analysis described below is compatible with “clinical breakage” as defined by Steiner et al.,7 whereas our definition of slippage includes incomplete slippage and is broader than “clinical slippage.”7 Upon returning to the clinic, the participant reviewed the experience in a brief follow-up interview, was given five condoms of the other type, and was instructed to complete five coital logs. After completing use of the second set of condoms, the participant returned five logs, participated in a final interview to describe the experience of using the second condom type, and completed a short questionnaire comparing the two products with respect to characteristics of the product and aspects of user satisfaction. Specifically, participants were asked to compare the acceptability of the two condoms with respect to the following criteria: 1) easy to learn how to use, 2) easy to put on, 3) feels natural during sex, 4) easy to keep on/in during sex, 5) easy to remove, 6) not messy, 7) does not interrupt sex, 8) makes sex enjoyable, and 9) feels good because it protects you. For each of the nine criteria listed above, the participant was asked to choose among the following ratings: 1 ⫽ S much better than X, 2 ⫽ S better than X, 3 ⫽ S slightly better than X, 4 ⫽ condoms equally good, 5 ⫽ X slightly better than S, 6 ⫽ X better than S, and 7 ⫽ X much better than S. These nine scores were employed in the acceptability assessment described in the analysis section below. Procedures and forms were reviewed and approved by the University
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of Alabama at Birmingham Institutional Review Board. Data Analysis The objectives of the analysis were: 1) to compare the rates of breakage, slippage, and other adverse effects experienced by the participants with the two condoms compared, and 2) to compare the acceptability of the two condoms. Univariate statistics and frequency distributions were employed for descriptive purposes. Differences in breakage and slippage rates between the condoms tested were evaluated employing simple methods for the analysis of count data. The distribution of couples according to the number of adverse outcomes was also evaluated to assess clustering of outcomes. Logistic regression models for repeated measurements8 were employed to compare the breakage and slippage rates of the two condoms while accounting for within-subject correlation of outcomes. In the latter models, we evaluated the effect of condom type and order of use (first condom used, second condom used, etc) while taking into account the correlation of outcomes among condoms used by the same subject. Acceptability was evaluated by examining the distribution of the nine preference scores described above. Bowker’s test of symmetry9 was adapted to test the null hypothesis that, if the two condoms were equivalent, scores that are equidistant from the neutral category (eg, 2 ⫽ X better than S and 6 ⫽ S better than X) should be selected with the same frequency. For the scores described in this article, the test statistic is approximately distributed as a 2 with 3 degrees of freedom. Protocol deviations that were documented during the study conduct were classified as major or minor. The analyses described above were repeated after exclusion of major deviations, only, and after exclusion of all deviations.
Results Recruitment and Follow Up The target number of eligible couples was successfully achieved by both centers, and eligibility and baseline data were available for all couples. Each couple, identified by a number from 1 to 104, was randomly pre-assigned to a sequence of condom use (ie, X-S or S-X). The list of assignments was compared with the use sequence reported by the participants. Discrepancies in the data that suggested protocol deviations were discussed with the clinical staff, and were resolved or confirmed after review of all information available. At one center, 27 couples were randomly assigned
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Table 1. Selected baseline characteristics of participant couples, by partner gender Characteristic Age (years): mean, median, range Age (years), % distribution ⬍25 25–29 30–39 40–49 ⱖ50 Y School (years) mean, median, range Education: % distribution by highest degree attained High school College Graduate school Race: % distribution by group White Black Hispanic Asian/Pacific Islander
to the X-S sequence, whereas 23 couples were assigned to the S-X sequence condom. The coital logs of one couple assigned to the S-X sequence indicate that the intended sequence was not followed, and the couple began with the X condom. At the other center, 25 couples were randomly assigned to the X-S sequence, whereas 29 couples were assigned to the S-X sequence. Instead of receiving only the initial set of five condoms, however, the first 50 couples enrolled received both sets of condoms and were instructed to begin use of the condom type specified by their random assignment. To correct this error in the protocol implementation, all couples were interviewed by telephone to ascertain their condom use pattern and were instructed to return all unused condoms. This procedure confirmed that most couples had followed the intended use sequence, and ensured that a large number of couples completed the first follow-up questionnaire before beginning the second set of five condoms. Several protocol deviations were detected, however, as follows. Six couples (three in each condom use sequence) began with the wrong condom type, but were otherwise compliant (ie, they used the entire first set of five condoms and completed the first follow-up questionnaire before beginning the second set); one couple assigned to the X-S sequence alternated condom types; and one couple assigned the S-X sequence used only one condom and withdrew from the study. Overall, 103 couples returned complete sets of coital logs and completed follow-up and exit questionnaires, whereas the couple who withdrew returned only the initial visit questionnaire and one coital log. We classified as major protocol deviations alternat-
Male partner (N ⴝ 102)
Female partner (N ⴝ 102)
34.1, 30, 22–90
31.4, 29, 21–48
13.7 29.4 31.4 20.6 4.9 15.9, 16, 12–24
14.7 38.2 28.4 18.6 0 15.6, 16, 12–24
36.3 39.2 24.5
29.4 51.0 19.6
87.3 9.8 1.0 2.0
84.3 9.8 2.0 3.9
ing condom types (one couple) and dropping out of the study with a limited number of condom uses (one couple). The first type of deviation may lead to misclassification of condom failure data, whereas the second type leads to unbalanced information and to the impossibility of evaluating within-subject differences in failure rates. These two couples used a total of five X condoms and six S condoms, reported no condom breakage, two slippages with the X condom, and one slippage with the S condom (all slippages were of ⬎1 inch). This information, however, was excluded from the main analysis. We classified as minor deviations instances in which couples did not follow the intended sequence of use and began with the wrong condom type, when no other deviations were present (seven couples).
Characteristics of the Study Group Tables 1 and 2 report selected results of the analysis of data from the 102 couples who did not experience major deviations from the protocol. The average age of the male partner was about 34 years, whereas the average age of the female partner was 31 years (Table 1). The difference in mean age was not unexpected but overstates the difference in age between partners of the same couple. The distribution across age categories and the median age are in fact only slightly different in the two gender groups. The study group was predominantly white (85%–90%) and highly educated (mean number of years of school: 16; 65%– 70% of both gender groups had a college or graduate school degree). Almost all of the respondents had experience with condom use, and 37% had experienced at least one condom breakage, suggesting that
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Table 2. Condom use experience of participant couples at baseline % distribution of couples (N ⴝ 102)
Characteristic Ever used a condom (responding partner only) Yes No Ever experienced condom breakage (responding partner only) Yes No No. of condoms used with the current partner during the last 30 days 0 1–4 ⱖ5
96.1 3.9 37.3 62.7 83.3 7.7 9.0
they had used a relatively large number of condoms in the past (Table 2). On the other hand, relatively few of the respondents (17%) had used condoms with their current partner during the previous 30 days (Table 2). Condom Breakage, Slippage, and Other Adverse Effects During Follow Up Of the 1020 condom logs evaluated, 14 reported a condom breakage: eight of 510 X condom logs (rate: 1.6 per 100 uses), and six of 510 S condom logs (rate: 1.2 per 100 uses) (Table 3). The two rates are very similar and statistically indistinguishable (Fisher’s exact test, two-tailed: p ⫽ 0.8). The point estimate of the X-S breakage rate difference is 0.4%, and its 95% confidence interval ranges from ⫺1.0% to ⫹ 1.8%, indicating that it is very unlikely that the true breakage rate of the X condom exceeds the breakage rate of the S condom by ⬎2%. Thus, the breakage rates are roughly equivalent. The number of breakages reported is too small to evaluate their distribution Table 3. Distribution of selected coital log items related to condom breakage, by condom tested (X ⫽ baggy; S ⫽ straight-shaft) Condom tested Coital log item Did the condom break? Yes No When did the condom break? While putting the condom on During sex While partner was withdrawing his penis While removing the condom
X N (%)
S N (%)
510 (100) 8 (2) 502 (98)
510 (100) 6 (1) 504 (99)
1 (12) 5 (63)
2 (33) 4 (67)
0 (0) 2 (25)
0 (0) 0 (0)
Table 4. Selective coital log items related to condom slippage, by condom tested (X ⫽ baggy; S ⫽ straight-shaft) Condom tested Coital log item Did the condom slip? Yes No Missing data How far did it slip? ⬍1 inch down the penis ⬎1 inch down the penis but not completely off the penis Slipped completely off the penis When did it slip? During sex before he ejaculated During sex after he ejaculated When he was withdrawing his penis Missing data Did you or your partner hold the base of the condom during withdrawal? Yes No Missing data
X N (%)
S N (%)
509 (100) 50 (10) 459 (90) 1 (0) 50 (100) 39 (78)
508 (100) 58 (11) 450 (89) 2 (0) 58 (100) 40 (69)
8 (16)
15 (26)
3 (6) 50 (100) 29 (58) 8 (16)
3 (5) 53 (100) 26 (49) 7 (13)
13 (26)
20 (38) 5
509 (100) 220 (43) 289 (57) 1
507 (100) 222 (44) 285 (56) 3
according to when the breakage occurred during intercourse. Condom slippage was reported in 50 X logs (rate: 9.8 per 100 uses) and in 58 S logs (rate: 11.4 per 100 uses) (Table 4). Slippage was most often partial (⬍1 inch) and may not indicate mechanical failure of the condom. The two rates of slippage were statistically indistinguishable (Fisher’s exact test, two-tailed, p ⫽ 0.42). The X-S difference in slippage rates is ⫺1.6%, and its 95% confidence interval ranges from ⫺5.4% to ⫹2.2%, indicating that it is very unlikely that the true slippage rate of the X condom exceeds the slippage rate of the S condom by more than two percentage points. Thus, it can be concluded that the overall slippage rates are roughly equivalent. If slippage of ⬍1 inch is excluded from the computations, the rates are reduced to 2.2% for the baggy condom and 3.5% for the straight shaft condom. These two “severe slippage” rates also were statistically indistinguishable (Fisher’s exact test, two-tailed, p ⫽ 0.19). The X-S severe slippage rate difference is ⫺1.4%, and its 95% confidence interval ranges from ⫺3.4% to ⫹0.7%, indicating that it is very unlikely that the true severe slippage rate of the X condom exceeds the slippage rate of the S condom by more than one percentage point. Within-couple clustering of condom slippage was more common than clustering of breakage. Only one
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Safety and Acceptability of a Baggy Condom
Table 5. Selective follow-up interview items related to other adverse effects
Table 6. Condom acceptability: selected exit interview ratings (N ⫽ 102)* 1 2 3
Condom tested Follow-up interview item Did you ever feel pain during intercourse because of the condom? Yes No Did you ever feel burning, itching, or irritation when using the condom? Yes No
X N (%)
S N (%)
102 (100) 4 (4) 98 (96)
102 (100) 6 (6) 96 (94)
102 (100) 9 (9) 93 (91)
102 (100) 16 (16) 86 (84)
of the 10 couples who reported condom breakage reported multiple breakages (N ⫽ 5), two with the X condom and three with the standard condom. Of 45 couples who reported at least one slippage, 26 (58%) reported more than one. Clustering of slippage seemed more frequent with the standard condom than with the X condom. Couples who reported slippage with one condom type also tended to report slippage with the other condom. Sixteen couples reported slippage of both condom types (as compared to 9.1 expected on the basis of the frequency of couples experiencing at least one slippage with the X condom, 32.4%, and the corresponding frequency for the S condom, 27.5%). Despite the evidence of clustering of slippage events, logistic regression analysis of breakage and slippage rates confirmed the results presented in Tables 3 and 4. After controlling for correlation of repeated condom uses, the effect of condom type was almost null, and order of condom use did not have a significant effect on either breakage or slippage (results not presented in detail). At follow-up interviews, adverse effects such as pain/discomfort, burning, itching, or other symptoms associated with irritation were reported slightly more frequently with the S condom than with the X condom (Table 5). None of these differences were statistically significant. User Preference The distribution of ratings displayed sufficient variability (ⱖ20%) for six of nine items for which respondents to the exit interview were asked to express a preference (Table 6). In most items, the distribution of ratings was in favor of the X condom, and was significantly skewed toward a preference for the X condom for four items: the new condom feels more natural during sex, is easier to keep on, is less disruptive, and makes sex more enjoyable. In none of the
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4
5
6
7
Acceptability item
N N N N N N N p value†
Easy to learn how to use Easy to put on/insert Feels natural during sex Easy to keep on/in during sex Easy to remove Not messy Does not interrupt sex Makes sex enjoyable Feels good because it protects you
2 0 1 2 4 5 0 2 1 1 3
2 96 1 0 1 0.88 7 69 17 3 3 0.15 8 32 22 21 10 0.0003
4 2 1 5 1 2 2 3 2 12
1 0
69 17 3 77 7 7 85 9 3 73 8 11 40 27 11
3 83
8
4
3 3 1 4 7
0.002 0.17 0.14 0.02 0.004
3 0.06
*Ratings: 1, S much better than X; 2, S better than X; 3, S slightly better than X; 4, condoms equally good; 5, X slightly better than S; 6, X better than S; 7, X much better than S. †Test of the hypothesis that ratings are symmetrically distributed on either side of the neutral score (4, condoms equally good).
acceptability items was there a statistically significant preference for the S condom. The analyses described above were repeated after excluding all protocol deviations or including all couples, and yielded results (not shown) that were virtually identical to the results presented above.
Discussion In the experience of the couples who participated in the study, the baggy condom was indistinguishable from a standard straight-shaft latex condom with respect to breakage, slippage, and other reported adverse effects. The rates of condom breakage and slippage are compatible with the relatively wide range of findings reported by other investigators,10 –24 who have reported breakage rates of 0.1–7.3% and slippage rates of 0.1– 6.6%. We recently published the results of a prospective observational study of the mechanical failure of the male condom among women attending sexually transmitted disease (STD) clinics, and reported a breakage rate of 2.3% and a slippage rate of 1.3%.25 Thus, although the breakage rates observed in the present study are relatively low, the slippage rates are high. We note that because of the careful data collection procedure, which requested information on slippage of ⬍1 inch, the results may not be comparable to those of other studies. If slippage of ⬍1 inch is excluded from the computations, the slippage rates are reduced to 2.2% for the baggy condom and to 3.5% for the straight shaft condom. These figures are very similar to those reported in the majority of published reports, including our own. Two potential limitations need to be considered in
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interpreting the results of this study. First, although recruitment was complete at both centers as planned, initial errors were made in implementing the study procedures, which made several protocol deviations possible. On the other hand, the deviations reported were minor, and it is unlikely that they could obscure a true difference in the failure rates of the two condoms compared. Second, as in most phase I/II studies, the study group was self-selected. Thus, the experience of the study group may not be representative of the general population. Furthermore, the group has a high baseline level of condom use and experience with breakage. On the other hand, the focus of the analysis was in the contrast between the two condoms tested, and internal validity, rather than generalizability of the findings, should be the key criterion in evaluating this study. The limitations discussed above are offset by the considerable strengths of the project. First, despite a few deviations, compliance with the protocol was remarkably high. All but one couple returned all coital logs and participated in the follow-up and exit interviews, lending credibility to the comparisons. Second, the randomized crossover design provides high credibility to inference about the comparison of breakage and slippage rates between the baggy condom and the standard straight-shaft condom used for comparison. Breakage and slippage rates appear to be no worse for the X condom as compared to the S condom, and the differences between breakage and slippage rates are small and statistically nonsignificant. In addition, the confidence intervals of the rate differences are relatively narrow. Thus, the information available supports the conclusion that the two condoms are equivalent with respect to breakage and slippage. Although simple statistical analyses of the data were sufficient to document the equivalence of the two condoms, more advanced techniques were used to explore the effect of within-couple correlation of outcomes. Logistic regression models for repeated measurements confirmed the results of simpler analyses. Finally, in contrast with the safety indicators, indicators of condom acceptability showed clear and statistically significant differences. The participants appear to prefer the X condom, suggesting that the new product may be more acceptable to the public than the traditional straight-shaft condoms available on the market, and may be easier to use consistently over long time periods. These features are likely to lead to higher typical use efficacy, even if the failure rates of the new condom are similar to those of other condoms.
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Acknowledgment This research project was carried out under contract with the manufacturer, who wishes to remain anonymous.
References 1. Warner DL, Hatcher RA. Male condoms. In: Hatcher RA, Trussell J, Stewart F, et al., eds. Contraceptive Technology, 17th Revised Edition. New York: Irvington Publishers, 1998. 2. Grinstead OA, Peterson, JL, Faigeles B, Catania JA. Antibody testing and condom use among heterosexual African-Americans at risk for HIV infection: The National AIDS Behavioral Surveys. Am J of Public Health 1997;87:857–9. 3. Abma J, Chandra A, Mosher W, Peterson L, Piccinino L. Fertility, family planning and women’s health: New data from the 1995 National Survey of Family Growth. Vital Health Stat 1997;23:7–114. 4. Michael RT, Wadsworth J, Feinleib J, Johnson AM, Laumann EO, Wellings K. Private sexual behavior, public opinion, and public health policy related to sexually transmitted diseases: A US-British comparison. Am J Public Health 1998;88:749 –54. 5. McCombs SB, McCray E, Frey RL, Onorata IM. Behaviors of heterosexual sexually transmitted disease clinic patients with sex partners at increased risk for human immunodeficiency virus infection. Sex Transm Dis 1997;24:461– 8. 6. Consumers Union. Can You Rely On Condoms? Consumer Reports 1989;54:134 – 41. 7. Steiner M, Trussel J, Glover L, et al. Standardized protocols for condom breakage and slippage trials: a proposal. Am J Public Health 1994;84:1897–9. 8. Diggle PJ, Liang K-Y, Zeger SL. Analysis of Longitudinal Data. Oxford: Oxford University Press, 1994. 9. Bowker AH. Bowker’s test for symmetry. J Am Stat Assoc 1948;43:572– 4. 10. Richters J, Donovan B, Gerofi J. How often do condoms break or slip off in use? Int J STD AIDS 1993;4:90-4. 11. van Griensven GJP, de Vroome EMM, Tielman RAP, Coutinho RA. Failure rate of condoms during anogenital intercourse in homosexual men. Genitourin Med 1988;64:344 – 6. 12. Golombok S, Sketchley J, Rust J. Condom failure among homosexual men. J Acquired Immun Defic Syndr 1989;2:404 –9. 13. Thompson JLP, Yager TJ, Martin JL. Estimated condom failure and frequency of condom use among gay men. Am J Public Health 1993;83:1409 –13. 14. Judson FN. Effectiveness of condoms for prevention of HIV infections. AIDS Updates 1989;2:1– 8. 15. de Graaf R, Vanwesenbeeck I, van Zessen G, Straver CJ, Visser JH. The effectiveness of condom use in heterosexual prostitution in The Netherlands. AIDS 1993;7: 265–9. 16. Albert AE, Hatcher RA, Graves W. Condom use and breakage among women in a municipal hospital family planning clinic. Contraception 1991;43:167–76. 17. Grady WR, Tanfer K. Condom breakage and slippage among men in the United States. Fam Plann Perspect 1994;26:107–12. 18. Richters J, Gerofi J, Donovan B. Why do condoms break
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or slip off in use? An exploratory study. Int J STD AIDS 1995;6:11– 8. 19. Gøtzsche PC, Hørding M. Condoms to prevent HIV transmission do not imply truly safe sex. Scand J Infect Dis 1988;20:233– 4. 20. Steiner M, Piedrahita C, Glover L, Joanis C, Spruyt A, Foldesy R. The impact of lubricants on latex condoms during vaginal intercourse. Int J STD AIDS 1994;5:29 –36. 21. Steiner M, Piedrahita C, Glover L, Joanis C. Can condom users likely to experience condom failure be identified? Fam Plann Perspect 1993;25:220 – 6.
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22. Golombok S, Shledon J. Evaluation of a thicker condom for use as a prophylactic against HIV transmission. AIDS Educ Prev 1994;6:454 – 8. 23. Zekeng L, Feldblum PJ, Oliver RM, Kaptue L. Barrier contraceptive use and HIV infection among high-risk women in Cameroon. AIDS 1993;7:725–31. 24. Sparrow MJ, Lavill K. Breakage and slippage of condoms in family planning clients. Contraception 1994;50:117–29. 25. Macaluso M, Kelaghan J, Artz L, et al. Mechanical failure of the latex condom in a cohort of women at high STD risk. Sex Transm Dis 1999;26:450 – 8.
Safety and Acceptability of a Baggy Latex Condom Maurizio Macaluso,* Richard Blackwell,† Bruce Carr,‡ Jareen Meinzen-Derr,* Michele Montgomery,* Micki Roark,‡ Murrill Lynch,† and Elizabeth M. Stringer† A total of 104 couples participated in a randomized crossover trial to compare a new baggy condom with a straightshaft condom produced by the same manufacturer. Participants completed a coital log after using each condom. All couples used five condoms of each type. Among 102 couples who did not report major deviations from the protocol, the breakage rate was eight of 510 (1.6%) for the baggy condom, and six of 510 (1.2%) for the standard condom (rate difference, RD ⫽ 0.4%, 95% confidence interval of the RD, CI ⫽ ⫺1.0%; ⫹1.8%). Slippage was reported in 50 baggy condom logs and in 58 standard condom logs; the slippage rate was 50 of 510 (9.8%) for the baggy condom, and 58 of 510 (11.4%) for the standard condom (RD ⫽ ⫺1.6%, 95% CI ⫽ ⫺5.4%; ⫹2.2%). Slippage was most often partial (⬍1 inch) and may not indicate condom failure. Severe slippage rates were 11 of 510 (2.2%) for the baggy condom, and 18 of 510 (3.5%) for the standard condom (RD ⫽ ⫺1.4%, 95% CI ⫽ ⫺3.4%; ⫹0.7%). The findings support the conclusion that the two condoms are equivalent with respect to breakage and slippage. The participants appeared to prefer the baggy condom, suggesting that the new product may be more acceptable to the public than the traditional straight-shaft condoms, and may be easier to use consistently over long time periods. CONTRACEPTION 2000;61:217–223 © 2000 Elsevier Science Inc. All rights reserved. KEY WORDS:
barrier contraception, contraceptive efficacy, phase I/II studies
Introduction
W
hen used consistently and correctly, the latex condom provides good protection against unintended pregnancy and against infection with sexually-transmitted pathogens, in-
*Department of Epidemiology and International Health, School of Public Health, University of Alabama at Birmingham, Birmingham, Alabama; †Department of Obstetrics and Gynecology, School of Medicine, University of Alabama at Birmingham, Birmingham, Alabama; and ‡Department of Obstetrics and Gynecology, School of Medicine, University of Texas Southwestern Medical Center, Dallas, Texas Name and address for correspondence: Dr. Maurizio Macaluso, UAB School of Public Health, MJH 108, 1530 3rd Ave South, Birmingham, AL 35294-2010; Tel.: (205) 934-7835; Fax: (205) 975-2435 Submitted for publication December 13, 1999 Revised February 7, 2000 Accepted for publication February 10, 2000
© 2000 Elsevier Science Inc. All rights reserved. 655 Avenue of the Americas, New York, NY 10010
cluding the human immunodeficiency virus (HIV).1 Despite large-scale efforts to encourage safer sex, consistent condom use is not widely practiced.2–5 For example, the latex condom was used as a contraceptive by only 19% of US women 15– 44 years of age who were at risk for pregnancy in the 1995 National Survey of Family Growth.3 The most common complaints among users are that condoms interrupt lovemaking and reduce sensation.6 Thus, the design and production of more acceptable condoms may play an important role in the promotion of condom use to larger segments of the population. Loose-fitting condoms seem to reduce interference with sensation during intercourse and may be more acceptable.1 We report the results of a phase I study of the acceptability and safety of a new baggy condom, compared with a standard straight-shaft condom.
Materials and Methods Study Design and Procedures To compare the newly designed baggy condom (X) with a straight-shaft, control condom (S) produced by the same manufacturer, we designed a prospective evaluation, according to a randomized cross-over design, of couples who used both condom types. A couple was eligible for participation in the study if the following conditions were met: 1) the woman’s age was 18 – 47 years; 2) the couple was in a mutually monogamous relationship during the previous 6 months; 3) the couple was using a method of birth control; 4) the couple was not using barrier contraception as the main birth control method; 5) neither partner had had sexually transmitted diseases during the previous 2 years; 6) neither partner was allergic to latex; 7) the couple maintained an average coital frequency of five acts of intercourse per month. A total of 100 couples were recruited at two centers. Four additional couples were added later at one center to compensate for known protocol deviations and to ensure that information would be obtained on a total of 500 condoms of each type. Interested subjects were recruited from among personnel at the participating centers and from the local communities ISSN 0010-7824/00/$20.00 PII S0010-7824(00)00097-4
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through advertising. Either partner was allowed to be the primary participant, but in most cases women responded to the advertising and participated in the study. The participant partner provided informed consent and was interviewed at entry to gather baseline information. Next, the paticipant was randomly assigned to begin either with the X condom or with the S condom. The two alternative use sequences are referred to as X-S and S-X. Each participant received five condoms of one type, and was instructed to complete a brief questionnaire for each condom used (referred to as the coital log) and to return the logs after completing use of the five condoms. The log requested detailed information about problems that may have occurred during intercourse. If condom breakage occurred, the participant was asked to report when the breakage was noted (while opening the package, during intercourse, before/after ejaculation, after withdrawal) and in which section of the condom (base, mid-section, tip). If slippage occurred, the participant was asked to report when it was noted (before entry, during intercourse, before/after ejaculation, during or after withdrawal), and the extent of the slippage (⬍1 inch down the penis shaft, ⬎1 inch but not completely off, or completely off the penis). The definition of breakage used in the analysis described below is compatible with “clinical breakage” as defined by Steiner et al.,7 whereas our definition of slippage includes incomplete slippage and is broader than “clinical slippage.”7 Upon returning to the clinic, the participant reviewed the experience in a brief follow-up interview, was given five condoms of the other type, and was instructed to complete five coital logs. After completing use of the second set of condoms, the participant returned five logs, participated in a final interview to describe the experience of using the second condom type, and completed a short questionnaire comparing the two products with respect to characteristics of the product and aspects of user satisfaction. Specifically, participants were asked to compare the acceptability of the two condoms with respect to the following criteria: 1) easy to learn how to use, 2) easy to put on, 3) feels natural during sex, 4) easy to keep on/in during sex, 5) easy to remove, 6) not messy, 7) does not interrupt sex, 8) makes sex enjoyable, and 9) feels good because it protects you. For each of the nine criteria listed above, the participant was asked to choose among the following ratings: 1 ⫽ S much better than X, 2 ⫽ S better than X, 3 ⫽ S slightly better than X, 4 ⫽ condoms equally good, 5 ⫽ X slightly better than S, 6 ⫽ X better than S, and 7 ⫽ X much better than S. These nine scores were employed in the acceptability assessment described in the analysis section below. Procedures and forms were reviewed and approved by the University
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of Alabama at Birmingham Institutional Review Board. Data Analysis The objectives of the analysis were: 1) to compare the rates of breakage, slippage, and other adverse effects experienced by the participants with the two condoms compared, and 2) to compare the acceptability of the two condoms. Univariate statistics and frequency distributions were employed for descriptive purposes. Differences in breakage and slippage rates between the condoms tested were evaluated employing simple methods for the analysis of count data. The distribution of couples according to the number of adverse outcomes was also evaluated to assess clustering of outcomes. Logistic regression models for repeated measurements8 were employed to compare the breakage and slippage rates of the two condoms while accounting for within-subject correlation of outcomes. In the latter models, we evaluated the effect of condom type and order of use (first condom used, second condom used, etc) while taking into account the correlation of outcomes among condoms used by the same subject. Acceptability was evaluated by examining the distribution of the nine preference scores described above. Bowker’s test of symmetry9 was adapted to test the null hypothesis that, if the two condoms were equivalent, scores that are equidistant from the neutral category (eg, 2 ⫽ X better than S and 6 ⫽ S better than X) should be selected with the same frequency. For the scores described in this article, the test statistic is approximately distributed as a 2 with 3 degrees of freedom. Protocol deviations that were documented during the study conduct were classified as major or minor. The analyses described above were repeated after exclusion of major deviations, only, and after exclusion of all deviations.
Results Recruitment and Follow Up The target number of eligible couples was successfully achieved by both centers, and eligibility and baseline data were available for all couples. Each couple, identified by a number from 1 to 104, was randomly pre-assigned to a sequence of condom use (ie, X-S or S-X). The list of assignments was compared with the use sequence reported by the participants. Discrepancies in the data that suggested protocol deviations were discussed with the clinical staff, and were resolved or confirmed after review of all information available. At one center, 27 couples were randomly assigned
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Table 1. Selected baseline characteristics of participant couples, by partner gender Characteristic Age (years): mean, median, range Age (years), % distribution ⬍25 25–29 30–39 40–49 ⱖ50 Y School (years) mean, median, range Education: % distribution by highest degree attained High school College Graduate school Race: % distribution by group White Black Hispanic Asian/Pacific Islander
to the X-S sequence, whereas 23 couples were assigned to the S-X sequence condom. The coital logs of one couple assigned to the S-X sequence indicate that the intended sequence was not followed, and the couple began with the X condom. At the other center, 25 couples were randomly assigned to the X-S sequence, whereas 29 couples were assigned to the S-X sequence. Instead of receiving only the initial set of five condoms, however, the first 50 couples enrolled received both sets of condoms and were instructed to begin use of the condom type specified by their random assignment. To correct this error in the protocol implementation, all couples were interviewed by telephone to ascertain their condom use pattern and were instructed to return all unused condoms. This procedure confirmed that most couples had followed the intended use sequence, and ensured that a large number of couples completed the first follow-up questionnaire before beginning the second set of five condoms. Several protocol deviations were detected, however, as follows. Six couples (three in each condom use sequence) began with the wrong condom type, but were otherwise compliant (ie, they used the entire first set of five condoms and completed the first follow-up questionnaire before beginning the second set); one couple assigned to the X-S sequence alternated condom types; and one couple assigned the S-X sequence used only one condom and withdrew from the study. Overall, 103 couples returned complete sets of coital logs and completed follow-up and exit questionnaires, whereas the couple who withdrew returned only the initial visit questionnaire and one coital log. We classified as major protocol deviations alternat-
Male partner (N ⴝ 102)
Female partner (N ⴝ 102)
34.1, 30, 22–90
31.4, 29, 21–48
13.7 29.4 31.4 20.6 4.9 15.9, 16, 12–24
14.7 38.2 28.4 18.6 0 15.6, 16, 12–24
36.3 39.2 24.5
29.4 51.0 19.6
87.3 9.8 1.0 2.0
84.3 9.8 2.0 3.9
ing condom types (one couple) and dropping out of the study with a limited number of condom uses (one couple). The first type of deviation may lead to misclassification of condom failure data, whereas the second type leads to unbalanced information and to the impossibility of evaluating within-subject differences in failure rates. These two couples used a total of five X condoms and six S condoms, reported no condom breakage, two slippages with the X condom, and one slippage with the S condom (all slippages were of ⬎1 inch). This information, however, was excluded from the main analysis. We classified as minor deviations instances in which couples did not follow the intended sequence of use and began with the wrong condom type, when no other deviations were present (seven couples).
Characteristics of the Study Group Tables 1 and 2 report selected results of the analysis of data from the 102 couples who did not experience major deviations from the protocol. The average age of the male partner was about 34 years, whereas the average age of the female partner was 31 years (Table 1). The difference in mean age was not unexpected but overstates the difference in age between partners of the same couple. The distribution across age categories and the median age are in fact only slightly different in the two gender groups. The study group was predominantly white (85%–90%) and highly educated (mean number of years of school: 16; 65%– 70% of both gender groups had a college or graduate school degree). Almost all of the respondents had experience with condom use, and 37% had experienced at least one condom breakage, suggesting that
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Table 2. Condom use experience of participant couples at baseline % distribution of couples (N ⴝ 102)
Characteristic Ever used a condom (responding partner only) Yes No Ever experienced condom breakage (responding partner only) Yes No No. of condoms used with the current partner during the last 30 days 0 1–4 ⱖ5
96.1 3.9 37.3 62.7 83.3 7.7 9.0
they had used a relatively large number of condoms in the past (Table 2). On the other hand, relatively few of the respondents (17%) had used condoms with their current partner during the previous 30 days (Table 2). Condom Breakage, Slippage, and Other Adverse Effects During Follow Up Of the 1020 condom logs evaluated, 14 reported a condom breakage: eight of 510 X condom logs (rate: 1.6 per 100 uses), and six of 510 S condom logs (rate: 1.2 per 100 uses) (Table 3). The two rates are very similar and statistically indistinguishable (Fisher’s exact test, two-tailed: p ⫽ 0.8). The point estimate of the X-S breakage rate difference is 0.4%, and its 95% confidence interval ranges from ⫺1.0% to ⫹ 1.8%, indicating that it is very unlikely that the true breakage rate of the X condom exceeds the breakage rate of the S condom by ⬎2%. Thus, the breakage rates are roughly equivalent. The number of breakages reported is too small to evaluate their distribution Table 3. Distribution of selected coital log items related to condom breakage, by condom tested (X ⫽ baggy; S ⫽ straight-shaft) Condom tested Coital log item Did the condom break? Yes No When did the condom break? While putting the condom on During sex While partner was withdrawing his penis While removing the condom
X N (%)
S N (%)
510 (100) 8 (2) 502 (98)
510 (100) 6 (1) 504 (99)
1 (12) 5 (63)
2 (33) 4 (67)
0 (0) 2 (25)
0 (0) 0 (0)
Table 4. Selective coital log items related to condom slippage, by condom tested (X ⫽ baggy; S ⫽ straight-shaft) Condom tested Coital log item Did the condom slip? Yes No Missing data How far did it slip? ⬍1 inch down the penis ⬎1 inch down the penis but not completely off the penis Slipped completely off the penis When did it slip? During sex before he ejaculated During sex after he ejaculated When he was withdrawing his penis Missing data Did you or your partner hold the base of the condom during withdrawal? Yes No Missing data
X N (%)
S N (%)
509 (100) 50 (10) 459 (90) 1 (0) 50 (100) 39 (78)
508 (100) 58 (11) 450 (89) 2 (0) 58 (100) 40 (69)
8 (16)
15 (26)
3 (6) 50 (100) 29 (58) 8 (16)
3 (5) 53 (100) 26 (49) 7 (13)
13 (26)
20 (38) 5
509 (100) 220 (43) 289 (57) 1
507 (100) 222 (44) 285 (56) 3
according to when the breakage occurred during intercourse. Condom slippage was reported in 50 X logs (rate: 9.8 per 100 uses) and in 58 S logs (rate: 11.4 per 100 uses) (Table 4). Slippage was most often partial (⬍1 inch) and may not indicate mechanical failure of the condom. The two rates of slippage were statistically indistinguishable (Fisher’s exact test, two-tailed, p ⫽ 0.42). The X-S difference in slippage rates is ⫺1.6%, and its 95% confidence interval ranges from ⫺5.4% to ⫹2.2%, indicating that it is very unlikely that the true slippage rate of the X condom exceeds the slippage rate of the S condom by more than two percentage points. Thus, it can be concluded that the overall slippage rates are roughly equivalent. If slippage of ⬍1 inch is excluded from the computations, the rates are reduced to 2.2% for the baggy condom and 3.5% for the straight shaft condom. These two “severe slippage” rates also were statistically indistinguishable (Fisher’s exact test, two-tailed, p ⫽ 0.19). The X-S severe slippage rate difference is ⫺1.4%, and its 95% confidence interval ranges from ⫺3.4% to ⫹0.7%, indicating that it is very unlikely that the true severe slippage rate of the X condom exceeds the slippage rate of the S condom by more than one percentage point. Within-couple clustering of condom slippage was more common than clustering of breakage. Only one
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Table 5. Selective follow-up interview items related to other adverse effects
Table 6. Condom acceptability: selected exit interview ratings (N ⫽ 102)* 1 2 3
Condom tested Follow-up interview item Did you ever feel pain during intercourse because of the condom? Yes No Did you ever feel burning, itching, or irritation when using the condom? Yes No
X N (%)
S N (%)
102 (100) 4 (4) 98 (96)
102 (100) 6 (6) 96 (94)
102 (100) 9 (9) 93 (91)
102 (100) 16 (16) 86 (84)
of the 10 couples who reported condom breakage reported multiple breakages (N ⫽ 5), two with the X condom and three with the standard condom. Of 45 couples who reported at least one slippage, 26 (58%) reported more than one. Clustering of slippage seemed more frequent with the standard condom than with the X condom. Couples who reported slippage with one condom type also tended to report slippage with the other condom. Sixteen couples reported slippage of both condom types (as compared to 9.1 expected on the basis of the frequency of couples experiencing at least one slippage with the X condom, 32.4%, and the corresponding frequency for the S condom, 27.5%). Despite the evidence of clustering of slippage events, logistic regression analysis of breakage and slippage rates confirmed the results presented in Tables 3 and 4. After controlling for correlation of repeated condom uses, the effect of condom type was almost null, and order of condom use did not have a significant effect on either breakage or slippage (results not presented in detail). At follow-up interviews, adverse effects such as pain/discomfort, burning, itching, or other symptoms associated with irritation were reported slightly more frequently with the S condom than with the X condom (Table 5). None of these differences were statistically significant. User Preference The distribution of ratings displayed sufficient variability (ⱖ20%) for six of nine items for which respondents to the exit interview were asked to express a preference (Table 6). In most items, the distribution of ratings was in favor of the X condom, and was significantly skewed toward a preference for the X condom for four items: the new condom feels more natural during sex, is easier to keep on, is less disruptive, and makes sex more enjoyable. In none of the
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4
5
6
7
Acceptability item
N N N N N N N p value†
Easy to learn how to use Easy to put on/insert Feels natural during sex Easy to keep on/in during sex Easy to remove Not messy Does not interrupt sex Makes sex enjoyable Feels good because it protects you
2 0 1 2 4 5 0 2 1 1 3
2 96 1 0 1 0.88 7 69 17 3 3 0.15 8 32 22 21 10 0.0003
4 2 1 5 1 2 2 3 2 12
1 0
69 17 3 77 7 7 85 9 3 73 8 11 40 27 11
3 83
8
4
3 3 1 4 7
0.002 0.17 0.14 0.02 0.004
3 0.06
*Ratings: 1, S much better than X; 2, S better than X; 3, S slightly better than X; 4, condoms equally good; 5, X slightly better than S; 6, X better than S; 7, X much better than S. †Test of the hypothesis that ratings are symmetrically distributed on either side of the neutral score (4, condoms equally good).
acceptability items was there a statistically significant preference for the S condom. The analyses described above were repeated after excluding all protocol deviations or including all couples, and yielded results (not shown) that were virtually identical to the results presented above.
Discussion In the experience of the couples who participated in the study, the baggy condom was indistinguishable from a standard straight-shaft latex condom with respect to breakage, slippage, and other reported adverse effects. The rates of condom breakage and slippage are compatible with the relatively wide range of findings reported by other investigators,10 –24 who have reported breakage rates of 0.1–7.3% and slippage rates of 0.1– 6.6%. We recently published the results of a prospective observational study of the mechanical failure of the male condom among women attending sexually transmitted disease (STD) clinics, and reported a breakage rate of 2.3% and a slippage rate of 1.3%.25 Thus, although the breakage rates observed in the present study are relatively low, the slippage rates are high. We note that because of the careful data collection procedure, which requested information on slippage of ⬍1 inch, the results may not be comparable to those of other studies. If slippage of ⬍1 inch is excluded from the computations, the slippage rates are reduced to 2.2% for the baggy condom and to 3.5% for the straight shaft condom. These figures are very similar to those reported in the majority of published reports, including our own. Two potential limitations need to be considered in
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interpreting the results of this study. First, although recruitment was complete at both centers as planned, initial errors were made in implementing the study procedures, which made several protocol deviations possible. On the other hand, the deviations reported were minor, and it is unlikely that they could obscure a true difference in the failure rates of the two condoms compared. Second, as in most phase I/II studies, the study group was self-selected. Thus, the experience of the study group may not be representative of the general population. Furthermore, the group has a high baseline level of condom use and experience with breakage. On the other hand, the focus of the analysis was in the contrast between the two condoms tested, and internal validity, rather than generalizability of the findings, should be the key criterion in evaluating this study. The limitations discussed above are offset by the considerable strengths of the project. First, despite a few deviations, compliance with the protocol was remarkably high. All but one couple returned all coital logs and participated in the follow-up and exit interviews, lending credibility to the comparisons. Second, the randomized crossover design provides high credibility to inference about the comparison of breakage and slippage rates between the baggy condom and the standard straight-shaft condom used for comparison. Breakage and slippage rates appear to be no worse for the X condom as compared to the S condom, and the differences between breakage and slippage rates are small and statistically nonsignificant. In addition, the confidence intervals of the rate differences are relatively narrow. Thus, the information available supports the conclusion that the two condoms are equivalent with respect to breakage and slippage. Although simple statistical analyses of the data were sufficient to document the equivalence of the two condoms, more advanced techniques were used to explore the effect of within-couple correlation of outcomes. Logistic regression models for repeated measurements confirmed the results of simpler analyses. Finally, in contrast with the safety indicators, indicators of condom acceptability showed clear and statistically significant differences. The participants appear to prefer the X condom, suggesting that the new product may be more acceptable to the public than the traditional straight-shaft condoms available on the market, and may be easier to use consistently over long time periods. These features are likely to lead to higher typical use efficacy, even if the failure rates of the new condom are similar to those of other condoms.
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Acknowledgment This research project was carried out under contract with the manufacturer, who wishes to remain anonymous.
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